1. Field of the Invention
The present invention relates generally to a double row taper-roller bearing and an assembling method thereof, and more particularly to a method of assembling a double row taper-roller bearing by controlling a negative axial gap. The present invention also relates to a wheel support structure and a method of assembling the same structure.
2. Related Background Art
In a conventional double row taper-roller bearing, the control of a negative axial (axial direction) gap has hitherto involved such a construction that two pieces of inner rings are disposed side by side on a cylindrical member facing to one single outer ring having two tapered track surfaces, and a spacer is interposed between two inner rings. More specifically, so to speak, two sets of completed taper-roller bearings are disposed side by side in the axial direction, the spacer is interposed therebetween, a pre-load is controlled by fastening the two bearings from the axial direction, and the double row taper-roller bearing is assembled.
The double row taper-roller bearing, however, tends to be a part of an apparatus using this type of bearing rather than a single unit of bearing, wherein an inner ring and an outer ring of the bearing are being made integral with the members which have supported so far the inner ring and the outer ring. For example, in the double row taper-roller bearing for the hub unit for fitting a wheel of an automobile, it has been proposed that the conventional inner ring and outer ring be united into one unit integral with a flanged member formed with a bolt hole, which has hitherto supported the inner ring and the outer ring and fixedly joined to the wheel or the car body.
What is proposed above is, however, unable to control in fact the negative axial gap and can be therefore neither assembled nor used.
FIG. 13 shows a double row taper-roller bearing 1 which has been broadly used so far for supporting the wheel. This double row taper-roller bearing 1 is constructed in such a way that a pair of inner rings 3, 3 are each so supported by a plurality of taper-rollers 4, 4 as to be rotatable on a minor-diameter side of one single outer ring 2. Double row outer ring tracks 5, 5 each taking a configuration of tapered concave surface are formed along an inner peripheral surface of the outer ring 2, and inner ring tracks 6, 6 each assuming a configuration of tapered convex surface are formed along outer peripheral surfaces of the respective inner rings 3, 3. The taper-rollers 4, 4 are sandwiched in between the outer ring tracks 5, 5 and the inner ring tracks 6, 6 in a state the rollers 4, 4 are so held by cages or holders 7, 7 as to be rollable. Further, combined seal rings 8, 8 are attached between an inner peripheral surface at two side ends of the outer ring 2 and outer peripheral surfaces of side ends of the inner rings 3, 3, thereby closing openings at two axial side ends of an air space 9 in which the taper-rollers 4, 4 are set.
The above-described double row taper-roller bearing 1, which has hitherto been widely used, is assembled in procedures shown in FIGS. 14 and 15. To be specific, at first, as shown in FIG. 14, the taper-rollers 4, 4 are arranged along circumferences of the inner rings 3, 3 in the state of being so held by the cages or holders 7, 7 as to be rollable. Then, the inner rings 3, 3 are inserted inside of the outer ring 2 while remaining in this state, and, as shown in FIG. 15, the taper-rollers 4, 4 are brought into contact with the outer ring tracks 5, 5 and the inner ring tracks 6, 6. Then, finally, the combined seal rings 8, 8 are attached between the outer peripheral surfaces of the side ends of the inner rings 3, 3 and the inner peripheral surface at the two side ends of the outer ring 2.
The double row taper-roller bearing 1 itself, which is shown in FIG. 13, has no particular problem. In recent years, however, for the purpose of reducing the number of assembly steps by decreasing the number of parts, a so-called third-generation hub unit structure has been contrived, wherein the double row taper-roller bearing for supporting the wheel is provided integrally with the hub for supporting and fixing the wheel. If this type of third-generation hub unit structure is adopted, a flange for supporting the wheel is provided on an outer peripheral surface of one side end of the hub body, and a first inner ring track taking a configuration of tapered convex surface and serving to configure the taper-roller bearing of the first row, is formed directly along an outer peripheral surface of an intermediate portion. Then, an inner ring, having a second inner ring track taking a configuration of tapered convex surface, for configuring the taper-roller bearing of the second row, is fixedly fitted to an outer portion of s small-diameter stepped portion formed on an outer peripheral surface of the other side end of the hub body.
In the case of this structure, the flange provided on the outer peripheral surface of the hub body becomes an obstacle, and the seal ring on the side of the flange can not be attached afterward. Accordingly, it is required that this seal ring be, before assembling the hub body and the outer ring together, fixedly fitted inside the side end of the outer ring. Then, it is necessary for the taper-rollers constituting the taper-roller bearing of the first row to be inserted into the hub body on the minor-diameter side of the outer ring while being kept in the state of being disposed along the inner peripheral surface of the outer ring. It might be required for smoothing this inserting operation that the taper-rollers do not shift on the minor-diameter side when performing the inserting operation. In the case of the prior art structure shown in FIG. 13, however, this problem does not occur, and therefore no contrivance against this problem is given.
It is a primary object of the present invention to provide a double row taper-roller bearing and a method of assembling a double row taper-roller bearing, which are, when in an assembly, capable of assembling and being assembled by controlling a negative axial gap after the assembly.
To accomplish the above object, according to a first aspect of the present invention, a double row taper-roller bearing comprising:
an outer ring having first and second track surfaces which are formed along an inner peripheral surface thereof and respectively configure some proportions of tapered shapes opened opposite to each other outwards in the axial direction;
a first inner ring member extending over an entire length of said outer ring in the axial direction and having a first outer track surface formed along an outer periphery thereof and configuring a part of a tapered shape, facing to said first track surface of said outer ring and opened in the same direction, a portion of the first inner ring member facing to said second track surface of the outer ring being formed as a fitting surface
a second inner ring member having a second outer track surface formed along an outer periphery thereof, facing to said second track surface of said outer ring and configuring a part of a tapered shape opened in the same direction, the second inner ring member being fixedly fitted on the fitting surface of said first inner ring member;
a first roller row including a plurality of taper-rollers interposed between said first track surface of said outer ring and said first outer track surface of said first inner ring member, and rolling while being kept in contact with said track surfaces, and a first holder for holding said first taper-rollers; and
a second roller row including a plurality of taper-rollers interposed between said second track surface of said outer ring and said second outer track surface of said second inner ring member, and rolling while being kept in contact with said track surfaces, and a second holder for holding said second taper-rollers.
According to a second aspect of the present invention, there is provided a method of assembling a double row taper-roller bearing comprising:
an outer ring having first and second track surfaces which are formed along an inner peripheral surface thereof and respectively configure some proportions of tapered shapes opened opposite to each other outwards in the axial direction;
a first inner ring member extending over an entire length of said outer ring in the axial direction and having a first outer track surface formed along an outer periphery thereof and configuring a part of a tapered shape, facing to said first track surface of said outer ring and opened in the same direction, a portion of the first inner ring member facing to said second track surface of said outer ring being formed as a fitting surface;
a second inner ring member having a second outer track surface formed along an outer periphery thereof, facing to said second track surface of said outer ring and configuring a part of a tapered shape opened in the same direction, the second inner ring member being fixedly fitted on the fitting surface of said first inner ring member;
a first roller row including a plurality of taper-rollers interposed between said first track surface of said outer ring and said first outer track surface of said first inner ring member, and rolling while being kept in contact with said track surfaces, and a first holder for holding said first taper-rollers; and
a second roller row including a plurality of taper-rollers interposed between said second track surface of said outer ring and said second outer track surface of said second inner ring member, and rolling while being kept in contact with said track surfaces, and a second holder for holding said second taper-rollers,
said method comprising, after assembling said outer ring, said first roller row, said first inner ring member and said second roller row, the steps of:
measuring a tentative axial gap, with a tentative bearing body being assembled by inserting, into an air space for inserting said second inner ring member formed between the fitting surface of said first inner ring member and said second roller row, a master for said second inner ring member having the known dimensions serving as a positive axial gap with respect to this air space; and
calculating dimensions of said second inner ring member, from which a desired negative axial gap is obtained based on the measured tentative axial gap, and selecting and assembling said desired second inner ring member on the basis of a result of the calculation.
It is another object of the present invention to provide a novel wheel support structure incorporating a double row taper-roller bearing, and an assembling method thereof.
To accomplish this object, according to a third aspect of the present invention, a wheel support structure including a fixed member to be fixed to a knuckle of a suspension system, and a hub for fitting a wheel, said structure comprising:
an outer ring integral with said fixed member and having first and second track surfaces which are formed along an inner peripheral surface thereof and respectively configure some proportions of tapered shapes opened opposite to each other outwards in the axial direction;
a first inner ring member integral with said hub, extending over an entire length of said outer ring in the axial direction and having a first outer track surface formed along an outer periphery thereof and configuring a part of a tapered shape, facing to said first track surface of said outer ring and opened in the same direction, a portion of the first inner ring member facing to said second track surface of said outer ring being formed as a fitting surface
a second inner ring member having a second outer track surface formed along an outer periphery thereof facing to said second track surface of said outer ring and configuring a part of a tapered shape opened in the same direction, the second inner ring member being fixedly fitted on the fitting surface of said first inner ring member;
a first roller row including a plurality of taper-rollers interposed between said first track surface of said outer ring and said first outer track surface of said first inner ring member, and rolling while being kept in contact with said track surfaces, and a first holder for holding said first taper-rollers; and
a second roller row including a plurality of taper-rollers interposed between said second track surface of said outer ring and said second outer track surface of said second inner ring member, and rolling while being kept in contact with said track surfaces, and a second holder for holding said second taper-rollers.
According to a fourth aspect of the present invention, there is provided a method of assembling a wheel support structure which includes a fixed member to be fixed to a knuckle of a suspension system, and a hub for fitting a wheel, said structure comprising:
an outer ring integral with said fixed member and having first and second track surfaces which are formed along an inner peripheral surface thereof and respectively configure some proportions of tapered shapes opened opposite to each other outwards in the axial direction;
a first inner ring member integral with said hub, extending over an entire length of said outer ring in the axial direction and having a first outer track surface formed along an outer periphery thereof and configuring a part of a tapered shape facing to said first track surface of said outer ring and opened in the same direction, a portion of the first inner ring member facing to said second track surface of said outer ring being formed as a fitting surface
a second inner ring member having a second outer track surface formed along an outer periphery thereof facing to said second track surface of said outer ring, and configuring a part of a tapered shape opened in the same direction, the second inner ring member being fixedly fitted on the fitting surface of said first inner ring member;
a first roller row including a plurality of taper-rollers interposed between said first track surface of said outer ring and said first outer track surface of said first inner ring member, and rolling while being kept in contact with said track surfaces, and a first holder for holding said first taper-rollers; and
a second roller row including a plurality of taper-rollers interposed between said second track surface of said outer ring and said second outer track surface of said second inner ring member, and rolling while being kept in contact with said track surfaces, and a second holder for holding said second taper-rollers,
said method comprising, after assembling said outer ring, said first roller row, said first inner ring member and said second roller row, the steps of:
measuring a tentative axial gap, with a tentative bearing body being assembled by inserting, into an air space for inserting said second inner ring member formed between the cylindrical surface of said first inner ring member and said second roller row, a master for said second inner ring member having the known dimensions serving as a positive axial gap with respect to this air space; and
calculating dimensions of said second inner ring member, from which a desired negative axial gap is obtained based on the measured tentative axial gap, and selecting and assembling said desired second inner ring member on the basis of a result of the calculation.
According to a fifth aspect of the present invention, a hub unit for an automobile, comprises a hub body, an inner ring member fixedly fitted on an outer portion of the hub body, an outer ring disposed along circumferences of the hub body and of the inner ring member, a plurality of taper-rollers provided between outer peripheral surfaces of the hub body and of the inner ring, and an inner peripheral surface of the outer ring, a first seal ring for hermetically sealing between an inner peripheral surface of one side end of the outer ring and an outer peripheral surface of an intermediate portion of the hub body, and a second seal ring for hermetically sealing between an inner peripheral surface of the other side end of the outer ring and an outer peripheral surface of a side end of the inner ring member. The hub body includes a flange, provided along an outer peripheral surface of one side end thereof, for supporting a wheel, a first inner ring track taking a configuration of tapered convex surface and directly formed along an outer peripheral surface of an intermediate portion thereof, for configuring the taper-roller bearing of a first row, and a small-diameter stepped portion provided on an outer peripheral surface of the other side end thereof. The inner ring member includes a second inner ring track, taking a configuration of tapered convex surface and formed along an outer peripheral surface thereof, for configuring the taper-roller bearing of a second row, and is fixedly fitted to an outer portion of the small-diameter stepped portion. The outer ring includes first and second outer ring tracks, each taking a configuration of tapered concave surface and formed along an inner peripheral surface thereof, for configuring the taper-roller bearings of the first and second rows. Some of the plurality of taper-rollers are disposed between the first inner ring track and the first outer ring track in a state of so being held by the first holder as to be rollable, and the remaining taper-rollers are disposed between the second inner ring track and the second outer ring track in a state of being sop held by the second holder as to be rollable. The first holder prevents the respective taper-rollers from coming off inwards in the diametrical direction in a state of holding some of the plurality of taper-rollers. The second holder prevents the respective taper-rollers from coming off outwards in the diametrical direction in a state of holding the remaining taper-rollers among the plurality of taper-rollers.
According to a sixth aspect of the present invention, a method of assembling a hub unit for an automobile according to the fifth aspect of the invention, comprises a step of holding some of a plurality of taper-rollers by a first holder and disposing the taper-rollers inside of a first outer ring track along an inner peripheral surface of an outer ring, a step of inserting a hub body inside of the outer ring in a state of fixedly fitting a first seal ring to an inner peripheral surface of one side end of the outer ring till a first inner ring track is positioned inwardly of some of the plurality of taper-rollers, a step of subsequently fitting the inner ring member to an outer portion of a small-diameter stepped portion of the hub body while being inserted inside of the outer ring in a state where the remaining taper-rollers among the plurality of taper-rollers are held along a circumference of a second inner ring track by a second holder, and a step of finally attaching a second seal ring between an outer peripheral surface of an end of the inner ring member and an inner peripheral surface of a side end of the outer ring.
In the thus constructed hub unit for the automobile and assembling method thereof according to the present invention, the novel third-generation hub unit incorporating the double row taper-roller bearing can be assembled at a high efficiency, and the cost for this type of hub unit can be also reduced.